Half-zirconocene anilide complexes: synthesis, characterization and catalytic properties for ethylenepolymerization and copolymerization with 1-hexene

Abstract

A number of half-zirconocene anilide complexes of the type Cp*ZrCl₂[N(2,6-R¹₂C₆H₃)R²] [R¹ = ⁱPr (1, 3), Me (2); R² = Me (1, 2), Bn (3)] and Cp*ZrCl[N(2,6-Me₂C₆H₃)Me]₂ (4) (Cp* = pentamethylcyclopentadienyl) were synthesized from the reactions of Cp*ZrCl₃ with the lithium salts of the corresponding anilide in diethyl ether at room temperature. All new zirconium complexes were characterized by ¹H and ¹³C NMR and elemental analysis. Molecular structures of complexes 1, 2 and 4 were determined by single crystal X-ray diffraction analysis. Upon activation with AlⁱBu₃ and Ph₃CB(C₆F₅)₄, complexes 1–4 exhibit good catalytic activity for ethylene polymerization, and produce polyethylene with a moderate molecular weight. Among these zirconium complexes, complex 1 shows the highest catalytic activity while complex 4 shows the lowest catalytic activity for ethylene polymerization. Complexes 1–3 also exhibit moderate catalytic activity for copolymerization of ethylene with 1-hexene, and produce copolymers with relatively high molecular weight and reasonable 1-hexene incorporation. In addition, the activation procedure of these catalyst systems were studied by ¹H NMR spectroscopy.